The present invention relates generally to a vehicle roof structure reinforced to prevent the roof from deforming due to bending stresses applied thereto. More particularly, the invention relates to a reinforcement for a vehicle roof structure with a sun-roof.
As is well known, the vehicle roof panel is supported by a vehicle body frame which might consist of a front roof rail, a rear roof rail and roof side rails. The roof panel is made from a relatively thin metal panel. Such roof panels must be reinforced across its central area. For reinforcing the central portion, one or more roof crossbars are provided extending laterally between the roof side rails. By means of such roof crossbars, satisfactory reinforcement can be obtained.
However, the weight of the roof is increased by the crossbar so that the overall vehicle body weight is increased. This will necessarily result in lower fuel economy and performance of the vehicle.
To keep the vehicle weight low and simultaneously obtain sufficient reinforcement, there has been proposed a roof structure incorporating one or more reinforcement ribs extending longitudinally along the vehicle. The reinforcement ribs are formed by a sheet metal pressing process or the like and effectively increase the stiffness of the roof panel. Thus, the vehicle roof panel with the pressed reinforcement ribs will be sufficiently strong to resist bending stresses applied thereto.
On the other hand, when the vehicle roof is provided with a sun-roof, the pressed reinforcement ribs are necessarily interrupted and must end at a point near the rear lateral edge of the sun-roof. As a result, the bending stress applied to the roof panel tends to be concentrated at the front ends of the reinforcement ribs to cause deformation of the roof panel at that point. Therefore, in practice, reinforcement with only pressed reinforcement ribs is not suitable for roofs with a sun-roof.